A major objective of the research is to investigate and exploit the empty viral capsids and incomplete particles of subgroup B human adenoviruses. Emphasis is given to in vitro studies of adenovirus assembly, especially with regard to DNA packaging. One goal is to elucidate mechanisms of sequential protein-DNA interactions which result in the compaction of DNA within the confines of the capsid and which determine the left end polarity of capsid DNA association in vivo. The transfection potential of an effective in vitro system for packaging DNA molecules in the capsid of an animal virus is also of interest. Parallel with this is further understanding of the biological activity of incomplete adenovirus particles in abortive infections. These incomplete particles contain the DNA sequences from the left end transformation-active region of the adenovirus genome. A second objective in this project is to develop methods for physical mapping and manipulation of viral genomes. Work thus far has centered on studies of branched DNA structures and the process of branch migration leading to strand displacements. Our efforts have recently led to a general method for site-directed deletion mutagenesis in closed circular DNA. Recombinant DNA technology has recently been pursued, resulting in plasmid-cloned sequences from the entire Ad 3 genome. Our objective is the application of these clones for the study of DNA packaging in vitro as well as for probes in experiments related to viral genome expression and transformation. Using the deletion mutagenesis method, we hope to identify the specific viral DNA sequences which direct entry of DNA into empty adenovirus capsids in vivo and in vitro.